Detection of Uric Acid in the Presence of Dopamine and High Concentration of Ascorbic Acid Using PDDA Modified Graphite Electrode

The properties of graphite electrode (Gr) modified with poly(diallyl dimethyl ammonium chloride) (PDDA) for the detection of uric acid (UA) in the presence of dopamine (DA) and high concentration of ascorbic acid (AA) have been investigated by cyclic voltammetry, differential pulse voltammetry and chronoamperometry. The polymer modified graphite electrode was prepared by a very simple method just by immersing the graphite electrode in PDDA solution for 20 minutes. The PDDA/Gr modified electrode displayed excellent electrocatalytic activity towards the oxidation of UA, DA and AA compared to that at the bare graphite electrode. The electrochemical oxidation signals of UA, DA and AA are well resolved into three distinct peaks with peak potential separations of 220 mV, 168 mV and 387 mV between AA‐DA, DA‐UA and AA‐UA respectively in cyclic voltammetry studies and the corresponding peak potential separations are 230 mV, 130 mV and 354 mV respectively in differential pulse voltammetry. The lowest detection limits obtained for UA, DA and AA were 1×10^?7 M, 2×10^?7 M and 800×10^?9 M respectively. The PDDA/Gr electrode efficiently eliminated the interference of DA and a high concentration of AA in the determination of UA with good selectivity, sensitivity and reproducibility. The modified electrode was also successfully applied for simultaneous determination of UA, DA and AA in their ternary mixture.     

RNA Modified Electrodes for Simultaneous Determination of Dopamine and Uric Acid in the Presence of High Amounts of Ascorbic Acid

A promising electrochemical biosensor was fabricated by electrochemical grafting of ribonucleic acid (RNA) at 1.8 V (vs. SCE) on glassy carbon electrode (GCE) (denoted as RNA/GCE), for simultaneous detection of dopamine (DA) and uric acid (UA) with coexistence of excess amount of ascorbic acid (AA). The electrode was characterized by X‐ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The RNA modified layer on GCE exhibited superior catalytic ability and anionic exclusive ability in comparison with the DNA modified electrode. Three separated anodic DPV peaks were obtained at 0.312, 0.168 and ?0.016 V for UA, DA and AA, respectively, at the RNA/GCE in pH 7.0 PBS. In the presence of 2.0 mM AA, a linear range of 0.37 to 36 μM with a detection limit of 0.2 μM for DA, and in the range of 0.74 to 73 μM with a detection limit of 0.36 μM for UA were obtained. The co‐existence of 5000 fold AA did not interfere with the detection of DA or UA. The modified electrode shows excellent selectivity, good sensitivity and good stability.     

Synthesis of magnetic molecularly imprinted polymer particles for selective adsorption and separation of dibenzothiophene

We are presenting an electrochemical sensor for the simultaneous determination of dopamine (DA) and uric acid (UA) in the presence of even high concentrations of ascorbic acid (AA). It based on a glassy carbon electrode modified with an electroactive film of polymerized dibromofluorescein. The electrochemical behaviors of DA and UA were studied by cyclic voltammetry using the modified electrode. It exhibits excellent electrocatalytic activity towards the oxidation of the two analytes. Most notably, the oxidation potentials differ by 180 and 200?mV between AA-DA and DA-UA, respectively. Thus, excellent selectivity towards the oxidation of DA and UA in the presence of even high concentrations of AA is accomplished. Under the optimum conditions, the anodic peak currents are linearly related to the concentrations of DA and UA in the range from 0.2 to 200?μmol?L^-1 and from 1.0 to 250?μmol?L^-1, respectively. The detection limits for DA and UA are 0.03?μmol?L^-1 and 0.2?μmol?L^-1, respectively (at an S/N of 3). The method has good selectivity and sensitivity and was successfully applied to the simultaneous determination of DA and UA in spiked human serum.

Silver Doped Poly(L‐valine) Modified Glassy Carbon Electrode for the Simultaneous Determination of Uric Acid,Ascorbic Acid and Dopamine

In this paper, a silver doped poly(L ‐valine) (Ag‐PLV) modified glassy carbon electrode (GCE) was fabricated through electrochemical immobilization and was used to electrochemically detect uric acid (UA), dopamine (DA) and ascorbic acid (AA) by linear sweep voltammetry. In pH 4.0 PBS, at a scan rate of 100 mV/s, the modified electrode gave three separated oxidation peaks at 591 mV, 399 mV and 161 mV for UA, DA and AA, respectively. The peak potential differences were 238 mV and 192 mV. The electrochemical behaviors of them at the modified electrode were explored in detail with cyclic voltammetry. Under the optimum conditions, the linear ranges were 3.0×10^?7 to 1.0×10^?5 M for UA, 5.0×10^?7 to 1.0×10^?5 M for DA and 1.0×10^?5 to 1.0×10^?3 M for AA, respectively. The method was successfully applied for simultaneous determination of UA, DA and AA in human urine samples.     

Selective Detection of Uric Acid in the Presence of Ascorbic Acid and Dopamine Using Polymerized Luminol Film Modified Glassy Carbon Electrode

Electrochemically polymerized luminol film on a glassy carbon electrode (GCE) surface has been used as a sensor for selective detection of uric acid (UA) in the presence of ascorbic acid (AA) and dopamine (DA). Cyclic voltammetry was used to evaluate the electrochemical properties of the poly(luminol) film modified electrode. Scanning electron microscopy (SEM) and atomic force microscopy (AFM) have been used for surface characterizations. The bare GCE failed to distinguish the oxidation peaks of AA, DA and UA in phosphate buffer solution (pH 7.0), while the poly(luminol) modified electrode could separate them efficiently. In differential pulse voltammetric (DPV) measurements, the modified GCE could separate AA and DA signals from UA, allowing the selective determination of UA. Using DPV, the linear range (3.0×10^?5 to 1.0×10^?3 M) and the detection limit (2.0×10^?6 M) were estimated for measurement of UA in physiological condition. The applicability of the prepared electrode was demonstrated by measuring UA in human urine samples.     

电聚合烟酰胺制备电化学传感器：同时测定多巴胺、尿酸和抗坏血酸

用循环伏安法（CV）选择不同电位区间来电聚合烟酰胺（NA）得到了两种聚合物膜修饰电极：poly-niacinamide/GCE (poly-NA/GCE)和poly- nicotinic acid /GCE (poly-NC/GCE)。这两电极都具有显著电化学催化作用,能明显地降低多巴胺（DA）、尿酸（UA）和抗坏血酸(AA)的氧化过电位,并在混合溶液中使这些物质的氧化峰电位距离足够大,可进行三物质的同时测定。poly-NC/GCE的电催化性能更好一些,用差分脉冲伏安法（DPV）测定抗坏血酸,线性范围为75–3000 µmol L-1,电流灵敏度为5.6 mA•L•mol-1;测定多巴胺,线性范围为0.37 – 16 µmol L-1,电流灵敏度为1140 mA•L•mol-1; 测定尿酸,线性范围为0.74 – 230 µmol L-1,电流灵敏度为102 mA•L•mol-1。该电极具有很高的灵敏度、选择性和抗污染能力。     

Simultaneous Determination of Ascorbic Acid,Dopamine and Uric Acid at Pt Nanoparticles Decorated Multiwall Carbon Nanotubes Modified GCE

A modified electrode was fabricated by electrochemically deposition of Pt nanoparticles on the multiwall carbon nanotube covered glassy carbon electrode (Pt nanoparticles decorated MWCNT/GCE). A higher catalytic activity was obtained to electrocatalytic oxidation of ascorbic acid, dopamine, and uric acid due to the enhanced peak current and well‐defined peak separations compared with both, bare and MWCNT/GCE. The electrode surfaces were characterized by scanning electron microscopy (SEM), X‐ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS). Individual and simultaneous determination of AA, DA, and UA were studied by differential pulse voltammetry. The detection limits were individually calculated for ascorbic acid, dopamine, and uric acid as being 1.9×10^?5 M, 2.78×10^?8 M, and 3.2×10^?8 M, respectively. In simultaneous determination, LODs were calculated for AA, DA, and UA, as of 2×10^?5 M, 4.83×10^?8 M, and 3.5×10^?7 M, respectively.     

Determination of Ascorbic Acid in the Presence of Uric Acid and Folic Acid by a Nanostructured Electrochemical Sensor Based on a TiO2 Nanoparticle Carbon Paste Electrode

A carbon paste electrode (CPE), modified with novel hydroquinone/TiO₂ nanoparticles, was designed and used for simultaneous determination of ascorbic acid (AA), uric acid (UA) and folic acid (FA). The magnitude of the peak current for modified TiO₂-nanoparticle CPE (MTNCPE) increased sharply in the presence of ascorbic acid and was proportional to its concentration. A dynamic range of 1.0–1400.0 μM, with the detection limit of 6.4 × 10^?7 M for AA, was obtained using the DPV technique (pH = 7.0). The prepared electrode was successfully applied for the determination of AA, UA, and FA in real samples.     

Graphene-Multiwall Carbon Nanotube-Gold Nanocluster Composites Modified Electrode for the Simultaneous Determination of Ascorbic Acid,Dopamine, and Uric Acid

In this paper, graphene-multiwall carbon nanotube-gold nanocluster (GP-MWCNT-AuNC) composites were synthesized and used as modifier to fabricate a sensor for simultaneous detection of ascorbic acid (AA), dopamine (DA), and uric acid (UA). The electrochemical behavior of the sensor was investigated by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and differential pulse voltammetry (DPV) techniques. The combination of GP, MWCNTs, and AuNCs endowed the electrode with a large surface area, good catalytic activity, and high selectivity and sensitivity. The linear response range for simultaneous detection of AA, DA, and UA at the sensor were 120–1,701, 2–213, and 0.7–88.3 μM, correspondingly, and the detection limits were 40, 0.67, and 0.23 μM (S/N?=?3), respectively. The proposed method offers a promise for simple, rapid, selective, and cost-effective analysis of small biomolecules.     

聚三聚氰胺-石墨烯复合膜修饰电极对多巴胺与尿酸的同时测定

采用循环伏安法制备了聚三聚氰胺-石墨烯复合膜修饰电极(poly-(MA)-ERGO/GCE)。研究了抗坏血酸(AA)、尿酸(UA)和多巴胺(DA)在该修饰电极上的电化学行为。结果表明,该修饰电极对AA、UA和DA均有良好的电化学响应,且三者的氧化峰在该修饰电极上可完全分离。据此建立了在大量AA存在下同时测定UA和DA的新方法。在优化条件下,微分脉冲伏安法(DPV)测定UA和DA的线性范围均为1.0×10~(-8)~5.0×10-6mol·L~(-1),检出限(3sb)均为5.0×10~(-9)mol·L~(-1)。     

Electrocatalytic activity of three-dimensional monolayer of 3-mercaptopropionic acid assembled on gold nanoparticle arrays

3-Mercaptopropionic acid (MPA) was assembled on gold nanoparticle arrays to form three-dimensional monolayer. The electrochemical behavior of small biomolecules such as NADH, ascorbic acid (AA), uric acid (UA) and dopamine (DA) on the as-prepared three-dimensional monolayer was studied. The cyclic voltammetric results indicated that three-dimensional MPA monolayer promoted the electron transfer between NADH and electrode, which was similar to two-dimensional MPA monolayer assembled on planar gold electrode. However, to the electrooxidation of AA, although two-dimensional MPA monolayer exhibited a blocking effect, three-dimensional MPA monolayer showed an obvious promotion. The catalytic activity of three-dimensional MPA monolayer towards UA and DA was also observed, which was attributed to its three-dimensional structure that might effectively prevent the poison of the electrode surface by the oxidation products.     

钯/聚苯胺纳米多层膜的制备及对抗坏血酸和多巴胺的催化氧化

采用脉冲电位法(PPSM)结合聚苯胺(PANI)的层层自组装制备了Pd/PANI交替沉积纳米多层膜, 并用于抗坏血酸(AA)和多巴胺(DA)的检测. 实验发现, 多层膜结构形貌及催化性能受前躯体K₂PdCl₆浓度、 脉冲条件及膜厚度等影响. 当K₂PdCl₆浓度为2×10^-3 mol/L, 阴极脉冲电位为-0.3 V, 阶跃次数为17时, 5层Pd/PANI修饰玻碳电极对AA和DA的催化性能最佳; 在0.1 mol/L磷酸盐缓冲液中, AA和DA的氧化峰明显分离[ΔE_p(AA, DA)=160 mV], 其峰电流与浓度分别在5×10^-5～4×10^-4和4×10^-5～1×10^-4 mol/L范围内呈较好线性关系, 实现了对AA和DA的同时测定. 该修饰电极具有良好的抗干扰性和稳定性.     

聚对氨基苯磺酸/碳纳米管复合膜修饰电极对尿酸与抗坏血酸的同时测定

通过在碳纳米管修饰玻碳电极表面电聚合的方法制备了聚对氨基苯磺酸/碳纳米管复合膜修饰电极(PABSA/CNT/GC),采用扫描电镜对电极形貌进行了表征。运用循环伏安法研究了尿酸(UA)和抗坏血酸(AA)在该修饰电极上的电化学行为,在pH7.0的PBS中,UA和AA分别在0.312、-0.025 V处产生灵敏氧化峰,与其在聚氨基苯磺酸和碳纳米管单层膜修饰电极上的电化学行为相比,两者的氧化峰电流显著增加,峰电位差(ΔEpa)达到337 mV,表明碳纳米管和聚合物产生协同增效作用,探讨了其作用机理。在优化实验条件下,建立了差分脉冲伏安法同时测定UA和AA的方法,UA、AA的线性范围分别为2.5×10-7~5.0×10-4、8.0×10-6~4.0×10-3mol/L,检出限分别为7.5×10-8、5.0×10-6mol/L。该方法用于尿样中UA和AA的测定,结果令人满意。     

Simultaneous determination of ascorbic acid,dopamine, and uric acid using a carbon paste electrode modified with multiwalled carbon nanotubes,ionic liquid,and palladium nanoparticles

We describe the modification of a carbon paste electrode (CPE) with multiwalled carbon nanotubes (MWCNT) and an ionic liquid (IL). Electrochemical studies revealed an optimized composition of 60 % graphite, 20 % paraffin, 10 % MWCNT and 10 % IL. In a next step, the optimized CPE was modified with palladium nanoparticles (Pd-NPs) by applying a double-pulse electrochemical technique. The resulting electrode was characterized by scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, cyclic voltammetry, and electrochemical impedance spectroscopy. It gives three sharp and well separated oxidation peaks for ascorbic acid (AA), dopamine (DA), and uric acid (UA), with peak separations of 180 and 200 mV for AA-DA and DA-UA, respectively. The sensor enables simultaneous determination of AA, DA and UA with linear responses from 0.6 to 112, 0.1 to 151, and 0.5 to 225 μM, respectively, and with 200, 30 and 150 nM detection limits (at an S/N of 3). The method was successfully applied to the determination of AA, DA, and UA in spiked samples of human serum and urine. Figure

The CPE was modified with multiwalled carbon nanotubes and an ionic liquid. After optimization the electrode was further modified with palladium nanoparticles. The resulting electrode gives three sharp and well separated oxidation peaks for ascorbic acid, dopamine and uric acid     

柠檬酸修饰电极对抗坏血酸、多巴胺和尿酸的同时检测

研究柠檬酸(CA)修饰玻碳电极(CA/GC)在抗坏血酸(AA)、多巴胺(DA)和尿酸(UA)混合体系中的循环伏安(CV)行为.结果表明,AA、DA和UA在CA/GC电极上氧化峰电流增大,且三者氧化峰电位明显分离(ΔEp(DA,AA)=170 mV,ΔEp(DA,UA)=130 mV,ΔEp(AA,UA)=300 mV).据此,可同时检测AA、DA和UA.在优化的实验条件下,AA、DA和UA的氧化峰电流与其浓度分别在2.0×10-6～1.5×10-3mol.L-1,6.0×10-7～1.0×10-3mol.L-1和6.0×10-7～1.0×10-3mol.L-1范围内呈线性关系.该电极重现性好,可用于盐酸多巴胺针剂DA、VC片剂AA及人体尿液UA的测定.     

Fabrication of layer-by-layer modified multilayer films containing choline and gold nanoparticles and its sensing application for electrochemical determination of dopamine and uric acid

A novel electrochemical sensor has been constructed by use of a glassy carbon electrode (GCE) coated with a gold nanoparticle/choline (GNP/Ch). Electrochemical impedance spectroscopy (EIS), field emission scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the properties of this modified electrode. It was demonstrated that choline was covalently bounded on the surface of glassy carbon electrode, and deposited gold nanoparticles with average size of about 100 nm uniformly distributed on the surface of Ch. Moreover, the modified electrode exhibits strong electrochemical catalytic activity toward the oxidation of dopamine (DA), ascorbic acid (AA) and uric acid (UA) with obviously reduction of overpotentials. For the ternary mixture containing DA, AA and UA, these three compounds can be well separated from each other, allowing simultaneously determination of DA and UA under coexistence of AA. The proposed method can be applied to detect DA and UA in real samples with satisfactory results.     

Uracil Grafted Carbon Electrode:Electrocatalytic Behavior of Tryptophan,Tyrosine, Catecholamine and Related Compounds

基于尿嘧啶作为一种碱基,具备一定的分子识别能力,制备了一种新颖的尿嘧啶共价修饰电极,用X射线光电子能谱和电化学方法进行了表征,并研究了酪氨酸、色氨酸、儿茶酚胺（如多巴胺,肾上腺素,去甲肾上腺素）及相关的化合物尿酸、抗坏血酸在该电极上的电化学行为,获得相应的氧化电位、电流灵敏度、线性范围和检测限等信息。其中,色氨酸检测线性范围：1.8 - 120 mM,检测限（s/n=3）：0.8 mM;酪氨酸检测线性范围：1.8 - 89mM,检测限（s/n=3）：0.8 mM。实验表明,尿嘧啶修饰电极能催化氧化上述电活性物质,但催化能力不同,据此,我们讨论了尿嘧啶与上述物质的相互作用,详细探讨了催化机理,扩展了对基于分子识别的传感器的研究。     

A Novel Functionalized Single‐Wall Carbon Nanotube Modified Electrode and Its Application in Determination of Dopamine and Uric Acid in the Presence of High Concentrations of Ascorbic Acid

Multilayer films of negatively charged single‐wall carbon nanotubes (SWCNTs) and positively charged cetylpyridinium bromide (CPB) have been deposited on a glassy carbon electrode (GCE) using layer‐by‐layer (LBL) technique. The assembled multilayer films have been investigated by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), and quartz crystal microbalance (QCM) measurements. The voltammetric signal of dopamine (DA), uric acid (UA), and ascorbic acid (AA) could be observed well‐separated with the assembled SWCNTs/CPB multilayer films in pH 7.0 PBS. The oxidation peak potentials of DA, UA, and AA are centered at about 169 mV, 292 mV and ?10 mV on differential pulse voltammograms (DPVs), respectively. The peak‐to‐peak potential separation was 123 mV, 179 mV, and 302 mV for DA‐UA, DA‐AA, and UA‐AA in DPVs, respectively. This permits the simultaneous detection of DA and UA in the presence of AA.     

DNA/Poly(p-aminobenzensulfonic acid) composite bi-layer modified glassy carbon electrode for determination of dopamine and uric acid under coexistence of ascorbic acid

A nano-composite of DNA/poly(p-aminobenzensulfonic acid) bi-layer modified glassy carbon electrode as a biosensor was fabricated by electro-deposition method. The DNA layer was electrochemically deposited on the top of electropolymerized layer of poly(p-aminobenzensulfonic acid) (Pp-ABSA). Scanning electron microscopy, X-ray photoelectron spectroscopy and electrochemical impedance spectrum were used for characterization. It demonstrated that the deposited Pp-ABSA formed a 2-D fractal patterned nano-structure on the electrode surface, and which was further covered by a uniform thin DNA layer. Cyclic voltammetry and electrochemical impedance spectrum were used to characterize the deposition, and demonstrated the conductivity of the Pp-ABSA layer. The biosensor was applied to the detection of dopamine (DA) and uric acid (UA) in the presence of ascorbic acid (AA). In comparison with DNA and Pp-ABSA single layer modified electrodes, the composite bi-layer modification provided superior electrocatalytic actively towards the oxidation of DA, UA and AA, and separated the originally overlapped differential pulse voltammetric signals of UA, DA and AA oxidation at the bare electrode into three well-defined peaks at pH 7 solution. The peak separation between AA and DA, AA and UA was 176 mV and 312 mV, respectively. In the presence of 1.0 mM AA, the anodic peak current was a linear function of the concentration of DA in the range 0.19-13 microM. The detection limit was 88 nM DA (s/n=3). The anodic peak current of UA was also a linear function of concentration in the range 0.4-23 microM with a detection limit of 0.19 microM in the presence of 0.5 mM AA. The superior sensing ability was attributed to the composite nano-structure. An interaction mechanism was proposed.     

Gold nanoparticles on a thiol-functionalized silica network for ascorbic acid electrochemical detection in presence of dopamine and uric acid

A simple preparation methodology able to stabilize gold nanoparticles and to obtain an electrode which detects ascorbic acid, uric acid, and dopamine by different techniques is presented. A 3-mercaptopropyl-functionalized silica network was synthesized using the sol–gel method. Gold nanoparticles (nAu) were immobilized on the material at synthesis by adding a sol of these previously prepared particles to the reaction mixture. The electrochemical behavior of the SiO₂/MPTS/Au carbon paste electrode was studied using cyclic voltammetry in the presence of a hexacyanoferrate probe molecule. The presence of nAu in the functionalized silica network changes the electrochemical characteristics of the material, favoring the electron transfer process of this complex ion. The SiO₂/MPTS/Au electrode was proven to be an efficient tool in the simultaneous determination of ascorbic acid (H₂AA), dopamine (DA), and uric acid (UA) using square wave voltammetry techniques. With the nAu on the electrode, an increase in the peak current related to the redox process of the H₂AA, DA, and UA was observed. The separations of the anodic peak potentials between DA/H₂AA and UA/H₂AA were 310 and 442?mV, respectively. The results obtained show that the SiO₂/MPTS/Au electrode can be used in the simultaneous determination of H₂AA, DA, and UA.